1. Field of the Invention
This invention relates generally to shredding machines, and more particularly to a lubrication distribution system within the shredding machine which provides a lubricating fluid to the cutting elements while they shred sheet materials.
2. Description of the Background Art
Most paper shredders employ a pair of counter-rotating rollers having a plurality of interleaved cutting elements. As shreddable material, such as paper, is fed between the counter-rotating rollers, the interleaved curing elements cut or tear the material into longitudinal strips using a scissor-like action. In many applications, such as governmental document destruction, this type of destruction proves inadequate because of the possibility that the content of the shredded documents can be reconstructed since characters remain on the longitudinal strips. Therefore, improved shredders have been developed which shred materials in both the longitudinal and lateral directions.
Although both types of shredders mentioned destroy documents satisfactorily, there are limitations to the rate at which material can be shredded. The "metal-to-metal" contact required to cut strips into segments causes a significant amount of wear on the cutting elements and rollers which reduces the shredding rate. More importantly, the repeated contact between the cutting elements and the shreddable material causes stress and heating on the curing surfaces of the curing elements. Over time, this continuous stress and thermal cycling at the cutting surfaces results in the dulling of the cutting elements which leads to shredder performance degradation. In addition to the reduction in shredding rate, the maintenance costs are increased and the overall service life of the shredding machine is reduced. Experimentation has shown that lubricating the cutting elements reduces the coefficient of friction between the moving parts and diminishes the thermal cycle to which the cutting surfaces are subjected due to the cooling effects of the lubrication fluid. The ultimate result of the lubrication process is a higher shredding capacity and an increased service life of the shredding machine.
In many mechanical systems employing cutting elements, it is typical to supply lubrication to those elements to reduce friction and resist the tendency to dull. However, this lubrication concept has not been widely utilized in shredding machines. U.S. Pat. No. 5,186,398 discloses a method and apparatus for lubricating the cutting elements of a shredding machine. First, the shafts mounting the cutting elements come to a complete stop which suspends the shredding process. Then, the shafts rotate in the reverse direction as oil from a pipe with discrete holes drips onto the cutting elements. After a predetermined period, the oil flow ceases and the shafts commence rotation in the forward shredding mode. Although this method of lubrication fulfills the need for lubrication, it creates an undesirable "down-time" in the shredder thereby diminishing the shredder system efficiency. Additionally, the pipe must be precisely manufactured such that the discharge holes evenly distribute the lubrication across the cutting elements.
In the unpatented "Automated Shredder Oiler" by Security Engineered Machinery of Massachusetts, the lubrication system is designed for retrofitting non- lubricated shredding machines. The AC electric cord of the shredding machine is plugged into the retrofit lubrication system which, in turn, is plugged into the electrical socket. As long as current is drawn by the shredder, the pump operates at a user-defined duty cycle and forces oil to a cloth-wrapped manifold while the shredding process is effectuated. The cloth is used to provide a more even distribution of the lubricating oil than a plain manifold with discrete holes. However, the cloth tends to become "baggy" at undetermined regions of the manifold upon saturation with oil causing oil accumulation in those baggy regions. Ultimately, the oil flow onto the cutting elements below those baggy regions is dramatically increased in comparison to other regions which is adverse to the desired result of an even distribution of oil. Additionally, the pump utilized is an automobile fuel pump which draws approximately 4 Amps which limits the current that can be allocated to the shredding machine. Furthermore, since the current draw of each type of shredding machine is unique, it is possible that the summation of the pump current and the shredder current will exceed the current capabilities of the source.